The conductivity of lower ionosphere deduced from sudden enhancements of strength (SES) of v.l.f. transmissions

Yamashita, Mineko

doi:10.1016/0021-9169(69)90104-4

Cited by 5 publications

(3 citation statements)

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“…The greater value of time lag between the sunrise at the third reflection point and the sunrise fade minimum in winter can be explained in terms of ionospheric parameters. In an undisturbed day the conductivity parameter at the reflection height of 70 km is about 2-5 x 104 s-1 [7]. The rate of ionization at a height h and zenith angle X is given by [ 12 ] V(X,h) o~e -r sec× (1) where r is the optical depth of the atmosphere down to the height h. In winter months × increases and along with it, the optical depth r and sec X increase.…”

Section: Discussionmentioning

confidence: 99%

“…Ionospheric probing using ground based facilities and frequencies in the region from ELF to LF involves the measurement of one or more parameters of the radio signal such as amplitude, phase and polarization as received at locations near to or far away from a radiation source [4]. Such measurements in the past have been widely used to observe or detect changes in the normal and disturbed ionization conditions due to solar flares, meteor showers and earthquakes upto and below E-region [5,6,7,8,9 ]. Sufficient informations on weak but widespread ionization in the D-region produced frequently after the magnetic storms has also been reported earlier [ 10].…”

Section: Discussionmentioning

confidence: 99%

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Meteorological effect on long distant 40 kHz signal

Sarkar

De²

1985

Arch. Met. Geoph. Biocl. A.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Meteorological effect on long distant 40 kHz signal

Sarkar

De²

1985

Arch. Met. Geoph. Biocl. A.

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“…The Fresnel's reflection coefficient R i of the lower boundary of the ionosphere is given by Yamashita (1969):…”

Section: 68mentioning

confidence: 99%

Effects of a Solar Eclipse on the Propagation of VLF-LF Signals: Observations and Results

De¹,

De²,

Bandyopadhyay³

et al. 2011

Terr. Atmos. Ocean. Sci.

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The results from the measurements of some of the fundamental parameters (amplitude of sferics and transmitted signal, conductivity of lower ionosphere) of the ionospheric responses to the 22 July 2009 solar eclipse (partial: 91.7%) are shown. This study summarizes our results from sferics signals at 81 kHz and subionospheric transmitted signals at 19.8 and 40 kHz recorded at Agartala, Tripura (latitude: 23°N, longitude: 91.4°E). We observed significant absorption in amplitude of these signals during the eclipse period compared to their ambient values for the same period during the adjacent 7 days. The signal strength along their propagation paths was controlled by the eclipse associated decrease in ionization in the D-region of the ionosphere. Waveguide mode theory calculations show that the elevation of the height of lower ionosphere boundary of the Earth-ionosphere waveguide to a value where the conductivity parameter was 10 6 unit. The absorption in 81 kHz sferics amplitude is high compared to the absorption in the amplitude of 40 kHz signal transmitted from Japan. The simultaneous changes in the amplitudes of sferics and in the amplitude of transmitted signals assert some sort of coupling between the upper atmosphere and the Earth's near-surface atmosphere prevailing clouds during solar eclipse.

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